The invention described herein relates to nuclear fuel processing systems and more particularly to an improved nozzle used in an ammonium diuranate (ADU) conversion line processing system. An ADU conversion process utilizes a packed column to hydrolize uranium hexafluoride gas with water to produce a uranyl fluoride solution containing hydrofluoric acid which subsequently is treated to extract uranium from the solution. In this kind of process, water admitted at the top of a column and gas into a side thereof mix to form a solution which eventually is discharged from the bottom of the column. Since the uranium hexafluoride gas will solidify or freeze at temperatures below about 147.degree. F., it is necessary that heat be imparted to a nozzle attached to the housing through which the gas flows to prevent such solidification during system operation, and particularly when the system is shut down for repairs or other purposes.
One design of gas nozzle used for this purpose includes a pair of concentrically disposed pipes secured at their midpoint to the column. The inner concentric pipe located outside the column is adapted for connection to a source of uranium hexafluoride gas which flows through the inner pipe into the column to be mixed with the water therein. The space between the concentric pipes carries steam which imparts its heat by conduction through the pipe walls to the gas to help assure maintaining the gas in a fluid state. The section of concentric pipes located inside the column turn downwardly toward the column bottom so that both gas and steam flowing through the pipes discharges from the nozzle end along the column axis.
The major disadvantage encountered in this nozzle design is that variation in steam flow occasionally permits the small sections of the nozzle pipes to drop below the gas freezing temperature. This action allows the uranium hexafluoride gas to freeze or solidify at different points along the pipe length and especially near the exit end thereof, thus causing plugging along the pipe length. Further, fluoride in the uranium hexafluoride gas forms hydrogen fluoride gas during the reaction which occurs when the gas comes in contact with moisture in the pipe. This further action corrodes the nozzle to such a great extent that the expected life is approximately two to three weeks, even though the pipe is constructed of stainless steel or other corrosion resistant materials of construction. Also, since the condition of the nozzle would cause steam flow to vary, the variation was suspected of causing detrimental effects to the uranium dioxide powder produced in the system.